Air-assist discharge of filter press cake

ABSTRACT

A filter press plate shifter assembly (21) provided with a shifter housing (22) having a tunnel-like center part which passes over the filter plates and housing parts positioned adjacent opposite side rails (14). Each side housing part mounts a pneumatic plate shifter (41) for permitting the endmost plate in the closed stack to be individually and sequentially shifted away from the stack into an open position when discharge of filtrate is desired. The shifter housing mounts a bumping device (61) which cooperates with the endmost plate in the stack to effect vertical bumping thereof relative to the support rails to assist in loosening sticky cake which adheres to the plate. The shifter housing also mounts an air-assist discharge mechanism (62) which includes a nozzle-bearing head assembly (80, 80&#39;) which moves vertically downwardly between the opposed faces of an open pair of adjacent plates for discharging airstreams downwardly against the plates to assist in removing the sticky cake from the plates. The overall operation of the shifter assembly is fully automated to permit each adjacent pair of plates in the closed stack to be opened, bumped and subjected to an air blast to cause discharge of sticky cake.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 07/952,236 filedSep. 28, 1992, now U.S. Pat. No. 5,328,617, and entitled AIR-ASSISTDISCHARGE OF FILTER PRESS CAKE.

FIELD OF THE INVENTION

This invention relates to a filter press and, more particularly, to aplate shifting mechanism for preferably automatically and sequentiallyshifting individual filter plates into an open position, with theshifting mechanism incorporating vibratory and air blow devices tofacilitate removal of filtrate, particularly sticky filtrate, from theopen filter plates.

BACKGROUND OF THE INVENTION

Filter presses are well known and extensively utilized for separatingsolids from slurries. Such presses employ a plurality of filter plateswhich are held in contacting relationship between fixed and movable headmembers while the slurry is pumped into and through the press forcollecting the solid in the form of filtrate or cake between adjacentfilter plates. When the press is full, then the movable head is backedaway from the plates into an open position, and in one type ofconventional press, the plates are then individually and sequentiallymoved into an open position adjacent the movable head to permitdischarge of the cake which has collected between the adjacent pairs ofplates. To permit movement of the plates into an open position, numerousplate shifting mechanisms have been provided for permitting eitherautomatic or manual control over the plate movement and cake discharge.

In the known filter presses, the plate shifter mechanisms often haverequired various manual controls or manual manipulations associated withthe movement of the plate shifter to effect sequential movement of theplates during opening thereof and dumping of the filter cake, althoughnumerous filter press assemblies have incorporated automatic shiftingmechanisms to permit such opening and dumping of the plates to besequentially automated. Most of the automated shifter assemblies,however, have required drive mechanisms such as chains or pressurecylinders positioned adjacent opposite sides of the press, which drivemechanisms themselves are generally elongate throughout substantiallythe entire length of the press and hence not only increase the overallsize and mechanical complexity of the press, but additionallysignificantly increase the overall cost of the press. These drivemechanisms are also typically disposed in areas where they are subjectto contamination by the material being handled. The filter pressesemploying automated plate shifters have thus possessed structural andfunctional features which have been less than desirable.

In addition, the known filter presses have also often operated in lessthan a satisfactory manner when utilized with materials which result ina filtrate or cake having "sticky" properties. That is, when dealingwith "sticky" cake, relying solely on gravity to cause discharge of thecake from between the opened filter plates is often insufficient toeffect proper discharge since the cake tends to stick to the filtercloths or membranes of the filter plates. It has been conventionalpractice to manually assist the discharge by having an operator scrapethe sticky cake from the filter plates by use of a paddle or the like.Needless to say, this is a very inefficient and time-consuming process.Further, satisfactory cleaning of the filter plates is difficult toachieve using this technique.

In an effort to improve the discharge of sticky cake, filter presseshave been developed and sold which have employed a vibrator, one suchpress being manufactured and sold by Perrin of Canada. In such press,the filter plates are joined together through a control device such as acable or linkage so that, during opening of the press, all of the platesare substantially simultaneously moved into an open separated conditionwith the spacing or separation between each adjacent pair of platesbeing controlled by the connecting linkage. All of the plates, adjacentone side thereof, are supported on an elongate tube which extendslongitudinally along the press and is of square or rectangular profile.This tube is then rotated so as to impose a vibration or bouncingmovement on the handles provided adjacent one side of the filter plates,whereby all of the plates are vibrated to assist in discharge of thesticky cake. While such arrangement is at least partially effective forpermitting discharge of sticky cake, nevertheless this is still ofundesirable structure since it requires an additional vibrating driveshaft extending longitudinally substantially throughout the length ofthe press, and in addition requires a long support frame or support railarrangement since all of the filter plates are moved into an open andspaced relationship at the same time.

While it is also known to equipped filter presses with liquid washingdevices for permitting cleaning of filter plates, nevertheless suchdevices are typically used only in a very controlled manner and inselected use situations, and typically are not used at the completion ofeach filter press cycle. More specifically, these washing devicestypically spray water on the opened filter plates so as to permitcleaning and flushing of the filter clothes, and hence such willnormally be done only infrequently, namely after a selected number offilter press cycles. Further, when such technique is used, it istypically not used to effect discharge of the filter cake since suchwould significantly increase the amount of liquid in the filter cake,and thus partially destroy the purpose of the filter press operation,namely the removal of liquid.

To improve upon filter presses employing a plate shifter assembly forpermitting automatic and sequential shifting of filter plates into openpositions during discharge of the press, the Assignee hereof hasdeveloped an improved press which is disclosed in copending U.S. Ser.No. 07/904,406, now U.S. Pat. No. 5,370,795. In the press of this latterapplication, the press is provide with an arch-type shifter housingwhich extends over and projects downwardly on both sides of the platesso that the downwardly projecting legs of the housing, adjacent lowerends thereof, are rollingly supported on the opposite elongate siderails of the press. Each of the side legs of the housing has a structurewhich mounts thereon a pneumatic plate shifter mechanism, and inaddition one of the housing side legs mounts a pneumatic drive motorwhich cooperates with a stationary elongate rod which extends parallelto the guide rail to effect driving movement of the housing and shiftermechanism longitudinally along the press. The entire operation,including the movement of the housing in a steplike manner along thepress, and the individual sequential shifting of the filter plates andthe synchronized movement thereof with the steplike movement of thehousing, is pneumatically operated, including a pneumatic logic controlfor controlling all of the pneumatic drive devices. The improved pressof this copending application is believed to represent a desirableimprovement over prior conventional structures, although the press ofthis prior application itself does not satisfactorily resolves theproblems associated with discharge of sticky cake. However, many of themechanisms associated with the shifter of the press of this priorapplication are incorporated into the present invention, and thedisclosure of copending U.S. application Ser. No. 07/904,406, now U.S.Pat. No. 5,370,795, is, in its entirety, incorporated herein byreference.

Accordingly, it is an object of this invention to provide an improvedfilter press which is particularly desirable for use with materialswhich create a sticky cake or filtrate, which improved filter pressgreatly facilitates the discharge of sticky cake and overcomes many ofthe disadvantages associated with prior filter presses.

More specifically, it is an object of this invention to provide animproved filter press which incorporates devices which subject thefilter plates to both a vibrating or bumping action to effect looseningof the sticky cake on the filter plates, and which thereafter subjectthe open filter plates to an air blow cycle to assist in discharging thesticky cake from the filter plates. The vibrating and air blowoperations are preferably sequentially carried out after one of anadjacent pair of filter plates has been moved into an open position toassist in effecting downward discharge of the sticky cake from betweenthe opened pair of filter plates, with the next filter plate thereafterbeing moved into an open position and the overall process being repeatedbetween the next pair of opened plates.

It is a further object of the invention to provide an improved filterpress, as aforesaid, having an improved filter plate shifting assemblywhich is of the arch-type so as to contain a drive associated with onlyone side of the filter press, without requiring driving elementsextending longitudinally along both sides of the press, which arch-typeshifter assembly also mounts thereon devices for effecting bothvibrating and air blowing of the filter plates as described above.

It is also an object of this invention to provide an improved filterpress which incorporates an air blast system which subjects the openfilter plates to an air blow cycle to assist in discharging cake fromthe filter plates. This air blow system, in a preferred embodiment,incorporates a plurality of discharge nozzles positioned closelyadjacent upper edges of the open filter plates to direct discharged highvelocity air downwardly against the cake to assist in loosening anddischarge of the cake, with the nozzles in the preferred embodimentbeing vertically displaceable downwardly along the open plates tosubject the cake to discharge assisting air either continuously or atselected intervals as the nozzles vertically traverse the open filterplates. In the preferred embodiment, the nozzles discharge air at avelocity which approaches at least supersonic speed, with the nozzleshaving an air accumulating tank associated therewith to permit thenozzles to emit a high velocity but short duration blast of air, withseveral such blasts preferably being emitted sequentially at short timeintervals as the nozzles traverse vertically of the filter plates.

Another object of the invention is to provide an improved filter press,as aforesaid, having a plate positioning and releasing arrangementassociated with the shifter housing to ensure that the filter platewhich is shifted into the open position may be disposed a predetermineddistance from the closed stack of plates so that the air dischargenozzles are properly positionally related with respect to the open sidesof the opposed filter plates, with the open plate then being moved anyremaining distance toward the movable head of the filter press after thecake discharge operation has been completed.

Other objects and purposes of the invention will be apparent to personsfamiliar with presses of this general type upon reading the followingspecification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art filter press.

FIG. 2 is a fragmentary side elevational view of the improved filterpress according to a first embodiment of this invention and showing theplate shifter assembly positioned for engagement with and shifting ofone of the filter plates in the stack when the press is in an openposition.

FIG. 3 is an enlarged side elevational view of the plate shifterassembly with a side cover of the shifter housing removed.

FIG. 4 is an end elevational view taken substantially from the leftwardend of FIG. 3.

FIG. 5 is an enlarged side elevational view of the lower part of theshifter housing, with an outer side cover removed to show interiordetails with respect to the plate shifter mechanism.

FIG. 6 is a fragmentary end elevational view, on an enlarged scale,showing a part of the right side of the arrangement shown in FIG. 4.

FIG. 7 is a top view of the arch-type shifter assembly.

FIG. 8 is a partial schematic of the control and driving system.

FIG. 9 is an end elevational view similar to FIG. 4 but illustrating avariation of the support and drive for the air blow device.

FIGS. 10A and 10B are views similar to FIG. 9 but illustrating a furthervariation of the air blow device.

FIG. 11 is a fragmentary side elevational view of a second and preferredembodiment of the invention, and specifically showing the press in anopen position with one of the filter plates being disposed in the opendischarge position spaced from the closed stack of plates just prior toinitiation of an air-assist discharge cycle.

FIG. 12 is an end elevational view as taken substantially from theleftward end of FIG. 11.

FIG. 13 is an enlarged sectional view of one of the air-assist dischargenozzle assemblies.

FIG. 14 diagrammatically illustrates the air-assist discharge nozzleassemblies as associated with the air-assist discharge head assembly,the air supply therefor, and the control thereof from the mastercontroller of the press.

FIG. 15 is a sectional view of a variation of the control pistonarrangement for the nozzle assembly of FIG. 13.

Certain terminology will be used in the following description forconvenience in reference only, and will not be limiting. For example,the words "upwardly", "downwardly", "rightwardly" and "leftwardly" willrefer to directions in the drawings to which reference is made. The word"forward" will refer to a direction of movement toward the fixed end ofthe press, namely rightwardly in FIGS. 1 and 2, and the word "rearward"will refer to the opposite movement direction. The words "inwardly" and"outwardly" will refer to directions toward and away from, respectively,the geometric center of the press and designated parts thereof. Saidterminology will include the words specifically mentioned, derivativesthereof, and words of similar import.

DETAILED DESCRIPTION

FIG. 1 illustrates a conventional filter press 11 having a frame 12which includes a pair of end frames or supports 13 rigidly joinedtogether by a pair of generally parallel and horizontally extending siderails 14 which are sidewardly spaced apart. The press includes a head 15which is movably supported on the rails 14 for movement toward and awayfrom a further head 16 (FIG. 2) which is fixedly secured adjacent theother end of the frame, with a plurality of conventional filter plates17 disposed between the heads so as to be held in clamped sealedrelationship to one another.

The filter press 11 also includes a plate shifter assembly 21 whichincludes a generally U-shaped or tunnel-like housing 22 defined bygenerally hollow housing parts 23 which are disposed adjacent theopposite side rails 14 and rigidly joined together by an arched centerpart 24 which projects upwardly so as to pass over the filter plates 17and the movable head 15. This shifter housing 22 is supported formovement horizontally longitudinally along the filter press, and forthis purpose is supported on elongate support rods 25 which are fixedlyjoined by hangers 26 to the respective side rails 14, whereby thesupport rods 25 are horizontally elongated in parallel relationship tothe rails 14 and are spaced sidewardly therefrom by a small distance.Each housing part 23 has a pair of rollers 27 (FIG. 3) provided thereonwhich are rollingly engaged with the respective rod 25 so that theentire shifter assembly 21 can be moved longitudinally along the presssubstantially as indicted by arrows 28.

Handles 18 associated with the filter plates 17 are disposed so as toproject outwardly from opposite sides of the individual filter plates atan elevation spaced downwardly from the upper edges of the filter platesso as to be slidably supported on the rails 14, whereby the individualfilter plates are disposed between and effectively suspended downwardlybetween the opposed side rails 14. The plates 17 in the filter press areof the type wherein each plate is defined by a generally rectangularouter frame which surrounds a cavity, with a pair of filter cloths ormembranes positioned generally so as to extend across the cavity, withthe filter cloths being individually carried on the rectangular frame.Such filter plates are of conventional construction, and one example ofsame is shown in U.S. Pat. No. 4,749,482.

The overall filter press having a general arrangement as described aboveis conventional. The present invention is directed to improvements in afilter press which incorporates the general structural and functionalrelationships described above, and such improvements are describedhereinafter with reference to FIGS. 2-8 which illustrate a firstembodiment of the invention.

To effect driving of the housing 22 longitudinally along the press, theone housing part 23, as illustrated by FIG. 5, has a drive unit 31mounted thereon. This drive unit 31 includes a grooved drive roller 32maintained in engagement with the upper side of the respective rod 25.The drive roller 32 is normally of a V-groove profile, and is preferablyconstructed of a plastic or rubberlike material so as to have highfriction and hence a secure rolling driving engagement with the rod 25.The drive roller 32 is driven from a motor 33, this being a direct drivein the illustrated embodiment, although the invention also contemplatesprovision of a speed reducer such as a gear or chain-type speed reducerbetween the motor shaft and the driven roller 32. The motor 33 is abi-directional air-driven rotary drive motor of conventionalconstruction. The motor is mounted interiorly of the tubular housingpart 23, and a drive shaft 34 (FIG. 6) for the roller 32 projectsoutwardly through the inner wall of the tubular housing part 23 so as toposition the roller 32 in driving engagement with the adjacent rod 25.The roller 32 may, if desired, be maintained in spring-urged drivingengagement with the rod, and one example of such arrangement isillustrated in aforementioned copending Ser. No. 07/904,406, now U.S.Pat. No. 5,370,795. The drive unit 31 is provided on only one of thehousing parts 23, the other side of the shifter housing 22 being free ofsuch drive unit.

A holding or braking device 35 (FIG. 5) is provided on one, andpreferably both, housing parts 23 for braking engagement with the rods25 when the drive unit 31 is de-energized. Each braking unit 35 includesa generally C-shaped yoke or carrier 36 disposed directly adjacent thesidewall-of housing part 23 and mounted thereon through vertical slots(not shown) so that the carrier 36 can undergo limited verticaldisplacement relative to the housing part 23. The C-shaped configurationof the carrier 36 is oriented so that it projects toward and partiallysurrounds the adjacent support rod 25, and a small air-actuated pressurecylinder 37 is mounted adjacent the upper end of the carrier 36 and hasthe piston rod thereof joined to an upper brake pad 38. A lower brakepad 39 is secured to the carrier 36 adjacent the lower end thereof. Thebrake pads 38 and 39 are respectively disposed directly over and underthe rod 25 and, when the cylinder 37 is pressurized, the upper pad 38 ispushed downwardly to react against the rod 25, thereby causing thecarrier 36 to shift upwardly so that the lower pad 39 also reactsagainst the rod 25, thereby creating a braking or holding engagementwith the rod 25 between the opposed pads 38 and 39. These pads arepreferably constructed of hard plastic and/or rubberlike materials. Aspring (not shown) is provided interiorly of the air cylinder 37 forreturning it to its retracted position, and a further spring (not shown)coacts with the carrier 36 for normally urging it towards its lowerposition to disengage the lower pad 39 from the rod 25.

Each housing part 23 of the shifter assembly 21 also mounts thereon aplate shifter 41 (FIG. 5) which includes a fluid pressure cylinder 42(herein referred to as the shift cylinder), preferably a double-actingair cylinder, having a conventional cylindrical housing 43 from one endof which a piston rod 44 slidably projects. The other end of cylinderhousing 43 is secured to a bracket 45 through a pivot or trunnion 46,the latter projecting horizontally in perpendicular relationship to thelongitudinal direction of the press so that the entire shift cylinder 42is vertically swingable about this pivot.

A first shifter member or blade 47 is fixedly secured to the free end ofthe piston rod 44, and a second shifter member or blade 48 is fixedlysecured to the end of the cylinder housing 43 through which the pistonrod projects. The shifter blades 47-48 are both platelike members whichextend transversely of the piston rod in generally parallel relationshipso as to substantially directly overlap when the piston rod is in theretracted position illustrated by FIG. 5.

The plate shifter 41 also includes a guide assembly defined by anelongate guide tube 49 fixed to and extending parallel along thecylinder housing 43, and an elongate guide rod 51 slidably supportedwithin the guide tube 49 with one end of rod 51 projecting outwardlythough the blade 48 for securement to the blade 47. Whenever the pistonrod 44 is extended, then guide rod 51 is also extended and preventsrotation of the blade 47.

The plate shifters 41 as disposed on opposite sides of the press arenormally maintained in lowered inactive positions, substantially asillustrated by dotted lines in FIG. 5. To move the plate shifter into araised positions for engagement with the filter press plates, whichraised position is indicated by solid lines in FIG. 5, there is provideda lifting mechanism 52 mounted in each housing part 23 for cooperationwith the respective plate shifter 41. The lifting mechanism 52 includesa lifting cylinder 53 which, like the shift cylinder 42, is adouble-acting pneumatic cylinder having a cylindrical housing 54 fixedrelative to the housing part 23 and a piston rod 55 slidably extendiblefrom the upper end thereof. This piston rod 55, at the upper free endthereof, has a suitable cap which abuts against the underside of a plate56 secured to the underside of the guide tube 49. Lifting cylinder 53 isnormally maintained in a lowered or contracted position illustrated bydotted lines in FIG. 5 to normally maintain the plate shifter 41 in thelowered inactive position. When lift cylinder 53 is energized to extendthe piston rod 55 upwardly, which upward extension is limited by aninternal stop, then the plate shifter 41 is moved into the operative orshifting position illustrated by FIGS. 3 and 5.

To position the plate shifter 41 in adjacent and proper positionalrelationship relative to the leading or endmost filter plate 17 in theclosed stack (i.e., the stack of plates which extends outwardly awayfrom the stationary head 16), the plate shifter assembly 21 on one sideof the housing 22 in the vicinity of but spaced upwardly from the blades47-48, is provided with a plate sensor 57 (FIG. 6). This plate sensor57, in the illustrated embodiment, comprises a conventional limit switchwhich is opened and closed by an elongate switching or sensing lever 58which is normally maintained (as by spring-urged) in a position whereinit projects inwardly within a generally vertical plane so as to bepositioned for contact with the handles 18 provided on one side of thefilter plates 17. When sensing lever 58 contacts one of the platehandles 18, the lever 58 is horizontally swung or displaced and causesactuation (i.e., opening) of the sensor 57 to effect stoppage of thedrive motor 33 of the shifter assembly 21.

To assist in removal of sticky sludge from the filter plates duringdischarge, the filter press of this invention as shown in FIGS. 3 and 4also incorporates a filter plate vibrating or bumping mechanism 61, andan air blow discharge assist mechanism 62, both of which are mounted onthe housing 22 of the shifter assembly so as to be movable therewith asthe shifter assembly effects sequential shifting of the filter platesinto an open discharge position.

Considering first the vibrating or bumping device 61, a pair of suchdevices 61 are provided, being disposed on the opposite side legs of thearch-shaped housing 22 so as to be positioned adjacent opposite sides ofthe press. Each device 61 includes a fluid pressure cylinder 63, namelya double-acting air cylinder, having a housing or cylinder 64 (FIG. 6)fixed to the shifter housing 22 and oriented so that the piston rod ofthe cylinder 63 projects vertically upwardly through the upper end forvertical extension. The piston rod of each bump cylinder 63 has theupper outer end thereof fixed to a generally L-shaped bump or impactmember 65 (FIG. 6) which includes a leg part 66 which projectsdownwardly and is vertically slidably guided along one side of thecylinder housing 64. This leg part 66 in turn has a bumping tab orprojection 67 projecting horizontally therefrom inwardly toward theadjacent upper corner of a filter plate 17. Each filter plate 17 is alsoprovided with a lifting bracket 68 fixedly secured to each upper cornerthereof. The lifting bracket includes a cantilevered lifting tab 69which projects horizontally outwardly in a sideward direction away fromthe upper corner of the filter plate, whereby the lifting tab 69projects so as to be disposed above and overlap the bumping tab 67, thelatter tabs being normally vertically spaced a small distance apart whenthe plates 17 are supported on the press rails 14 by the handles 18 andthe bump cylinders 63 are in their retracted (i.e., lowered) positions.

The bump cylinders 63 are mounted on the shifter housing 22 at aposition whereby the bump tabs 67 are sidewardly aligned directly underthe lifting tabs 69 associated with the front or endmost filter plateassociated with the closed stack, such as the filter plate designated173 in FIG. 3.

The bump cylinders 63 are normally maintained in the lower retractedposition and are activated only during the discharge cycle of the press.When the press is in the discharge cycle, pressurized air is rapidly andalternately supplied first into the lower ends and then into the upperends of the bump cylinders 63, which cycle is preferably repeated two orthree times in rapid succession, to cause at least two rapid cycles oflifting and lowering of the endmost filter plate 17₂ relative to theadjacent plate 17₃. This lifting is illustrated by the dotted lineposition of the filter plate in FIG. 6. The lifting is normally no morethan about two inches, and occurs with sufficient rapidity so as toeffectively result in free fall of the lifted filter plate until thehandles 18 of the lifted plate contact the press rails 14 and impose abump or impact on the plate which is effective in at least partiallyloosening the sticky filtrate or cake which is adhered to the plate. Thevertical displacement of the plate 17₂ relative to adjacent plate 17₃also assists in effecting at least partial loosening of the stickyfiltrate relative to the filter cloths of the adjacent filter plates.

Considering now the air blow discharge assist mechanism 62, andreferring specifically to FIGS. 3 and 4, this mechanism is mounted on agenerally arch-shaped or tunnel-like shroud 71 which is fixed to one endof the shifter housing 22 and projects longitudinally along the press ina direction toward the movable head 15 so as to effectively enclose atleast opposite sides of the gap or discharge region defined between theopposed pair of opened plates, such as represented by the plates 17₁ and17₂ in FIG. 3. This shroud 71 effectively comprises and constitutes anextension of the shifter housing 22 in that it includes a top wall 72which extends sidewardly across the press in upwardly spacedrelationship from the filter plates, and a pair of sidewall portions 73which project downwardly from the top wall 72 adjacent opposite sides ofthe press in sideward straddling relationship to the filter plates.

The discharge assist mechanism 62 includes a pressure cylinder 75,preferably a double-acting pneumatic cylinder. This pressure cylinder75, herein referred to as the blow or discharge cylinder, includes acylinder housing 76 which has a lower end thereof secured to a mountingplate 77, the latter being fixed to support arms 78 which are fixed toand project outwardly from the top wall of the shifter housing 22. Thedischarge cylinder 75 is vertically oriented and has the piston rod 79thereof disposed so as to slidably project vertically downwardly throughthe lower end thereof, which piston rod 79 in turn is coupled to an airdischarge head assembly 80 which includes a manifold block or nozzlehead member 81 which is horizontally elongated transversely (i.e.,perpendicularly) across the press. This manifold block 81 has atransversely extending length which is of a magnitude similar to thewidth of the filter plates.

The manifold block 81 also has a pair of vertically upwardly projectingguide rods 82 fixed thereto in straddling relationship to the piston rod79. These guide rods 82 are vertically slidably supported in bearingblocks 83 secured to the mounting plate 77, and the upper free ends ofthe guide rods 82 are joined together by a connecting plate 84.

The transversely extending manifold 81 has rows of air discharge nozzles85 projecting outwardly from opposite sides thereof so that the nozzles85 of one row project generally toward the exposed face of the openfilter plate (such as plate 17₁), and the nozzles 85 of the other rowproject generally toward the exposed face on the endmost filter plate ofthe closed stack (such as plate 17₂). The opposed rows of nozzles 85project horizontally outwardly in opposite directions from the manifold81 through a sufficient extent longitudinally of the filter press sothat the discharge ends of the nozzles 85 are positioned closelyadjacent the exposed faces of the opposed open filter plates 17₁ and 17₂when the manifold 81 is moved vertically downwardly into the gap orregion between the opposed opened filter plates, as explained below.

The manifold 81 has air passages (not shown) disposed interiorly thereoffor communication with the nozzles 85, which nozzles are disposed withina generally transverse horizontally extending row in substantiallyuniformly spaced relationship so that a plurality of nozzles aredisposed closely enough together to effect discharge of several adjacentairstreams against the exposed face of the filter plate, with theairstreams traversing downwardly during operation of the dischargeassist mechanism 62. The manifold 81 is supplied with pressurized airthrough an air supply conduit 86, the lower end of the which is fixed tothe manifold 81. The upper end of conduit 86 is fixed to the connectingplate 84 so that the conduit 86 is vertically displaceable in unisonwith the guide rods 82. A flexible air supply hose or conduit 87 has oneend thereof coupled to the upper end of supply conduit 86, and the otherend of hose 87 couples to an air supply conduit 88 which is fixed to theshifter housing 22.

The shifter housing 22 mounts thereon a control housing, indicateddiagrammatically at 89 in FIG. 3, the latter being surrounded by asuitable cover 91. The control housing contains therein the pneumaticand electrical controls for operation of the shifter, with the pneumaticcontrols (including valves and other conventional pneumatic controldevices) being supplied with pressurized air in a conventional mannerfrom an exterior pressure source.

As illustrated by FIGS. 3 and 4, the discharge cylinder 75 normallymaintains the air discharge head assembly 80 (namely the manifold 81 andnozzles 85) in an upper inactive position wherein this air dischargehead assembly 80 is spaced upwardly from the upper edges of the filterplates 17. The air discharge head assembly 80 is maintained in thisupper position by closing off the discharge cylinder 75 so that air islocked in the cylinder to maintain the piston rod in the upwardlycontracted position. During air-assisted discharge of filtrate from thefilter plates, however, then cylinder 75 is energized to extend the headassembly 80 downwardly into the gap between the opposed and spaced pairof opened plates and, during this downward traverse, air is constantlydischarged through the nozzles 85 so that a plurality of airstreams aredirected against and moved vertically downwardly across the exposedfaces of the filter plates to assist in discharging the sticky filtrate.The air discharge head assembly 80 moves downwardly a sufficient strokeso as to effectively traverse the complete face of the filter plates,and then the discharge cylinder 75 is reversed and moved upwardly to itsupper position, at which time the air supply to the manifold 81 isterminated and the cylinder 75 is pneumatically held in its raisedposition.

Referencing now FIG. 8, there is diagrammatically illustrated pneumaticand electrical control relationships associated with the shifter so asto effect automatic sequencing of the shifter assembly 21 tosequentially effect discharge of cake from between adjacent pairs offilter plates. More specifically, pressurized air is supplied from anexternal source 92, such as a compressor, through a main control valveV₁, the latter controlling the supply pressurized air to the press. Onevalve V₂ is provided for controlling flow of air to the two supply portsof the motor 33 so as to not only control energization of the motor 33,but also the direction of rotation thereof. A valve V₃ controls flow ofair to the double-acting bump cylinders 63, a valve V₄ controls flow ofair to the double-acting lift cylinders 53, a valve V₅ controls flow ofair to the brake cylinders 37, a valve V₆ controls flow of air to thedouble-acting shift cylinders 42, a valve V₇ controls flow of air to thedouble-acting discharge cylinder 75, and a valve V₈ controls flow of airto the manifold 81. These valves are of conventional configuration, andare typically electrically-actuated by appropriate signals received froma master press controller 93, the latter preferably comprising amicroprocessor. The controller 93 provides appropriate control signalsdesignated i through p to the valves V₁ through V₈ respectively so as tocontrol the operation thereof.

The controller 93 in turn receives appropriate signals designated athrough h from position sensing switches associated with the variouspneumatic drivers, specifically the air cylinders 42, 53, 63 and 75.

More specifically, each bump cylinder 63 has position sensors such asmagnetically-actuated reed switches S₁ and S₂ associated therewith forsensing the respective extended and contracted positions, with the twoswitches S₁ being connected in series, and the two switches S₂ connectedin series, whereby each cooperating pair emits a control signal a or bto the controller 93 only when both cylinders 63 are in the respectiveextended or contracted positions.

Similarly, the lifting cylinders have switches S₃ and S₄ (such asmagnetic reed switches) which designate the respective extended andcontracted positions, with switches S₃ being connected in series andemitting a control signal c to controller 93 only when both liftcylinders are extended, and similarly switches S₄ being connected inseries to emit a control signal d to controller 93 only when both liftcylinders are in the lowered or contracted positions.

The shift cylinders 42 have position sensors formed as switches S₅ andS₆ (such as Hall effect sensors) which respectively define the extendedand contracted positions of the shift cylinders 42. The two switches S₅are connected in series, as are the two switches S₆, and theserespectively emit control signals e and f to the controller 93.

Lastly, pressure cylinder 75 has position sensors S₇ and S₈, againnormally formed as magnetic-actuated reed switches, for respectivelyindicating the upper retracted and lower extended positions. Theseswitches in turn emit control signals g and h to the controller 93.

The controller 93 emits control signals to the various valves, such asV₁ through V₈, in response to control signals a through h as receivedfrom the various air cylinders so as to ensure proper automaticsequencing of the various devices and mechanisms.

The controller 93 also receives a signal from the position sensor 57when the latter contacts and is activated by the handle 18 on theendmost filter plate 17 of the stack so as to effect stoppage of thedrive motor 33.

The press 11 is also normally provided with appropriate position sensorssuch as limit switches LS1 and LS2 disposed adjacent opposite ends ofthe support rod 25, which limit switches sense the presence of theshifter housing 22 when it reaches the end positions so as to controlthe shifter assembly 21. For example, limit switch LS1 is normallydisposed adjacent the leftward end of the press in FIG. 1 so as tofunction as a "home" sensor to normally maintain the shifter assembly 21in a stationary "home" position adjacent this end of the press, such asduring the filling cycle of the press. The other limit switch LS2 isdisposed adjacent the other end of the press, namely the rightward endin FIG. 1, to sense when the shifter assembly 21 has moved along andeffected sequential opening of all of the plates, whereupon the switchLS2 effects reversal in the rotation driving of motor 33 so as to returnthe entire shifter assembly 21 to its home position.

There is preferably provided an additional switch S_(t) which iseffectively a start switch which can be manually activated if desired soas to permit initiation of the press opening and discharge cycle.

The operation of the filter press of the present invention, as explainedabove, will now be briefly described to ensure a complete understandingthereof.

The shifter assembly 21 will normally be maintained at the leftwardmostend (FIGS. 1 and 2) of the press, this being the normal home position.When emptying of the press is desired, a signal will be transmitted tothe press controller 93, either manually from the start switch S_(t) orfrom a portion of an automatic controller, such as a microprocessor,which controls the overall press operation. Controller 93 then suppliesa signal to valve V₂ to effect opening thereof so that pressurized airwill be supplied to motor 33 to effect "forward" rotation thereof. Thisdrives roller 32 and causes the entire shifter assembly 21 to moveforwardly (rightwardly in FIGS. 1 and 2) along the rods 25 until theshifter housing 22 passes over the head 15 (which has already been movedinto an open position wherein it is spaced a predetermined distance fromthe endmost movable filter plate 17₁) and over the endmost ones of theclosed stacked filter plates 17. In this regard, the endmost filterplate 17₁ is normally fixed to and moves with the movable head 15. Whenthe shifter assembly 21 approaches the endmost movable plate 17₂, theplate sensing lever 58 contacts the handle 18 of the endmost plate andis angularly deflected through a small angle. This activates the platesensor 57 so as to transmit a signal to the controller 93 which thenstops the motor 33. A signal m is emitted to the valve V₅ whichenergizes the brake cylinder 37 so as to apply the brake devices 35.After a predetermined but short time delay as controlled by thecontroller, the controller 93 then emits a signal k to valve V₃ whichpermits cyclic up-and-down actuation of the bump cylinders 63,preferably for at least two up-and-down cycles. That is, the controller93 emits appropriate signals to valve V₃ so as to cause rapid extensionfollowed by rapid contraction of the cylinders 63, this being performedpreferably at least twice in rapid sequence. This causes the bump tabs67 to engage the filter plate lifting tabs 69 and effect rapid upwardlifting of solely the endmost filter plate 17₂ a small distance,followed by downward dropping of the plate 17₂ against the rails 14 dueto the rapid retraction of the cylinders 63. This cycle is preferablyrepeated at least two times in sequence. During this cyclic lifting andlowering of the filter plate 17₂, the downwardly free fall of the plateand its impact on the rails 14, which is referred to herein as verticalbumping of the filter plate, is effective for causing at least partialdislodgement or loosening of the sticky cake which is adhered to notonly the exposed face of the plate 17₂, but also to the face of plate17₂ which faces the adjacent plate 17₃. This bumping of the plate hasbeen observed to effect sufficient loosening to create a slight gapbetween the sticky cake and the filter cloth, particularly adjacent theupper perimeter of the cloth and cake. After the controller 93 completesthe cyclic activation of the bump cylinders 63, and return of the bumpcylinders to the lower retracted positions is sensed by the positionsensors S₂ so as to emit a control signal b to the controller 93, thenthe controller 93 emits an appropriate control signal o so as toactivate the air discharge assist device 62.

More specifically, valve V₇ is activated to supply air to the upper endof blow cylinder 75, and simultaneously valve V₈ is activated to supplyair to the manifold 81. The head assembly 80 is then moved downwardlyinto the gap between the opposed open plates 17₁ and 17₂. The nozzles 85are disposed closely adjacent the opposed faces of the open filterplates, and in fact the nozzles are preferably oriented so they eject aplurality of sidewardly adjacent airstreams which are directed outwardlybut downwardly (such as at an angle of about 45°) toward the opposedexposed face of the filter plate. These airstreams are able to enterinto the narrow gaps created between the filter cake and the underlyingfilter cloth and effectively assist in peeling the sticky filter cakeaway from the filter cloth. As the head assembly 80 is loweredvertically downwardly between the opposed filter plates throughoutsubstantially the vertical extent thereof, these airstreams are directedoutwardly and downwardly generally into the interface region between thesticky cake and the filter cloth so as to effectively progressively peelthe filter cake away from the cloth as the nozzles move verticallydownwardly. Of course, the weight of the cake itself may additionallyassist in peeling away the sticky cake as a greater portion of the cakeis peeled outwardly away from the underlying filter cloth.

After the head assembly 80 reaches it lowermost position, then positionsensor S₈ emits a signal h to controller 93 which emits a control signalto valve V₇ so as to reverse flow of pressurized air to blow cylinder75, thereby causing the cylinder 75 and the head assembly 80 to beretracted upwardly into their uppermost position as illustrated by solidlines in FIG. 3. During this upward retraction, however, air iscontinually supplied to manifold 81 so as to effect further blowing ofairstreams against the opposed filter plates to effect some additionalsupplemental cleaning thereof, if necessary. Upon reaching the uppermostposition, position sensor S₇ emits a signal g to the controller whichthen deactivates the appropriate valves to hence deactivate supply ofpressure fluid to the cylinder 75 and manifold 81, whereby the cylinderis pneumatically locked in the raised position.

Upon receipt of signal g at the controller, the controller then emits asignal l so that valve V₄ is controlled to supply pressurized air to thelower ends of lifting cylinders 53 to effect extension thereof. When thecylinders 53 effect upward lifting of the plate shifter 41 into itsupper position, as sensed by the position sensors S₃, then a signal c istransmitted to the controller 93 which in turn then emits a signal tocontrol the valve V₆ of the shift cylinders 42. At this time, the shiftblades 47-48 have the upper ends thereof inserted into the narrow gapbetween the handles 18 of the endmost pair of closed plates 17₂ and 17₃.Energization of cylinders 42 results in the movable shifting blades 47being projected outwardly (leftwardly in FIGS. 3 and 5) toward themovable head 15, whereby the movable blades 47 contact the side handles18 on the endmost plate 17₂ so as to slide this filter plate along therails 14 toward an open position adjacent the head 15. When the shiftcylinders 42 reach their fully extended positions, the shifted plate 17₂is disposed in an open position wherein it abuts the plates stackedagainst the movable head 15, and is spaced a predetermined longitudinaldistance from the endmost plate 17₃ of the closed stack. During thisextension of the shift cylinders 42, the stationary blade 48 will, ifnecessary, due to slight shifting of the housing 22, react against theadjacent plate 17₃ to prevent any significant movement of the shifterhousing 22. When the controller 93 receives the signal e indicating fullextensions of the shifter cylinders 42, then the controller 93 signalsvalve V₆ so that the shift cylinders 42 are retracted, followed bylowering of the lift cylinders 53. The lowered lift cylinders 53 emit acontrol signal d to controller 93 which signals completion of thedischarge cycle for one pair of plates.

The controller 93 will initiate a new cycle by transmitting appropriatesignals which release the brake devices 35 and which again energize themotor 33 to effect forward rotation until the switching sensor 58contacts the handle of the next adjacent plate 17₃, whereupon thecomplete cycle is again automatically carried out in the same manner asdescribed above.

The shifting and discharge cycles continue until the last movable filterplate 17 is shifted and discharged of filtrate, at which time theshifter housing is again moved forwardly until contacting the limitswitch LS2, at which time the controller signals the motor 33 so thatthe rotational direction is reversed. This causes the entire shifterassembly 21 to then be moved rearwardly (leftwardly in FIGS. 1 and 2)along the rods 25 until the shifter assembly reaches its home positionas sensed by the switch LS1 which then deactivates the shifter assemblyuntil such time as a new start signal is received.

It will be understood that the filtrate or cake as discharged from theplates is deposited into a suitable collecting bin or the like asdisposed below the press.

The pneumatic and electrical controls illustrated in FIG. 8 are onlypartially and schematically shown since it will be understood that thespecific valves, switches and other related controlling devices arethemselves conventional, and can assume many different configurations soas to still provide the desired control functions, as will be readilyapparent to those of ordinary skill in such technology.

While the blow discharge assist mechanism 62 as described above, whereinthe vertically-extending blow cylinder 75 is provided for controllingthe vertical cycling movement of the discharge head assembly 80, isdesirable from a structural and operational simplicity standpoint, itwill be appreciated that such arrangement also does require significantoverall height in order to have all of the moving components verticallyaligned. Thus, other drive mechanisms can be provided for controllingvertical cyclic movement of the head assembly 80. Examples of additionaldrives for the blow discharge assist mechanism are illustrated in FIGS.9 and 10.

More specifically, in FIG. 9 the head assembly 80 is driven by andconnected to a pair of elongate chains 101 which abut back-to-back wherethey connect centrally to the manifold 81. The chains 101 projectupwardly and individually pass over driven counter-rotating drivesprockets 102 which are rotatably supported on the shifter housing at anelevation above the filter plates. These drive sprockets cause thechains 101 to retract horizontally, either sidewardly of the press orlongitudinally thereof, into appropriate guide tracks indicateddiagrammatically at 103. The chains 101 are of the type which arecapable of effecting driving both by pushing and pulling. That is, thelinks of the chain have direct solid abutments therebetween which permitpushing forces to be transmitted along the chain, and which permit thechain links to hinge only in a single direction away from the straightline condition, whereby when the chains are disposed in back-to-backrelationship, hinging of the chains is effectively prevented and thechains can thus provide a rather rigid link for controlling theup-and-down movement of the manifold head. The construction of suchchain is conventional. The sprockets can be driven through suitablegears by a single reversible drive motor if desired, which drive motorcan be controlled by appropriate signals received from the controller93.

The arrangement of FIG. 9 is desirable for use in those situations whereminimal height is available, since such transversely (i.e.,horizontally) projecting drive arrangement enable the overall height ofthe press to be reduced.

FIGS. 10A and 10B illustrated another variation of a drive device forthe air discharge assist mechanism 62, which modified drive device isalso of minimal height. In this embodiment, the mechanism 62 includes adouble-acting pneumatic cylinder 104 which is oriented horizontally inthe sideward direction of the press so that the piston rod is slidablehorizontally transversely of the press along the centerline 105. Thepiston rod of the cylinder 104 projects outwardly from one end and has abracket 106 secured thereto, the latter being coupled by a pivot 107 tothe upper free end of one upper link 108 of a scissor mechanism 109,specifically a lazy tong mechanism. This mechanism 109 includes afurther upper link 110 pivotally joined to link 108 by central pivot111, and the upper end of the link 110 is joined by a pivot 112 to astationary bracket 113 secured to the shifter housing. Links 108, 110 inturn have the lower ends thereof pivotally joined to respective upperends of links 114 and 115, the latter being centrally joined by a pivot116, and having their lower ends pivotally joined at 117 and 118 to asupport bar 119 which mounts and extends lengthwise along the manifold81 of the head assembly 80. The connection of pivot 118 to the support119 involves a slide member 121 which is movable lengthwise along thesupport bar 119 when the mechanism 109 is moved from the raisedcontracted position of FIG. 10A to the lowered extended position of FIG.10B.

Reference will now be made to FIGS. 11-14 which illustrate a secondembodiment of a filter press according to the present invention, whichembodiment incorporates therein a preferred variation of the air blowdischarge assist mechanism 62'. This discharge assist mechanism 62' isused in place of the discharge assist mechanism 62 described above.Corresponding parts of the discharge assist mechanism 62' and of thepress are designated by the same reference numeral utilized above exceptfor the addition of a prime (') thereto.

In the air blow discharge assist mechanism 62', the head assembly 80' isvertically moved by a scissor mechanism 109' which effects downwardvertical displacement of the head between the opened plates, followed byupward displacement into an upper inactive position, with this scissormechanism being utilized in this embodiment to permit minimization inoverall height. The head assembly 80' includes a horizontally elongatehead member 131 which extends traversely of the press and is fixedlysecured to a lower support rail 119' of the scissor mechanism bysuitable brackets 132. Two rows of nozzle assemblies 133 are provided onthe head assembly, with one row being on each side thereof and orientedso as to cooperate with an adjacent one of the two opposed filter platesdisposed in an opened position and from which the filtrate or cake is tobe removed. Each of these rows has a plurality of substantiallyidentical nozzle assemblies 133 disposed in uniformly spacedrelationship therealong, with five such nozzle assemblies being providedin each row in the illustrated embodiment.

The nozzle assembly 133 is formed as an air blaster for emitting a highvelocity but short duration air jet, such as a pulse of high velocityair, and preferably employs a converging-diverging nozzle of the typecommonly known as a Laval nozzle, so that the discharged air is at avery high velocity. Such Laval nozzles are generally designed to achievevelocities which approach or exceed sonic velocity.

Referencing FIG. 13, there is illustrated a construction of the nozzleassembly 133 so as to provide this desired blast or pulse function. Thisnozzle assembly 133 includes a closed storage tank 134 defining thereina closed chamber 135 of limited capacity, which chamber 135 in a typicalexample will have a volume which is significantly less than one cubicfoot, and in fact the volume of this chamber will more typically be inthe neighborhood of about 0.1 to about 0.5 cubic foot for supplying onenozzle. A pipe or tube 136 is positioned closely adjacent (and in theillustrated embodiment penetrates) the tank 134 and includes an airsupply part 137 at one end which joins to a control part 138 adjacentthe other end, this latter part 138 terminating in a flange 139 which isfixedly secured to the tank, as by fasteners 141. An air supply passage142 extends through the part 137 and opens into one end of an enlargedcylindrical chamber 143 as formed in the control part 138. A pluralityof ports or openings 144 extend radially through the part 137 forproviding controlled communication from the passage 142 into the chamber135, and for this purpose suitable check valves and more specificallyball valves 145 are sealingly seatable against the outer ends of theports 144 to selectively close off the ports and function as one-waycheck valves to prevent reverse flow from the chamber 135 back into thepassage 142. A suitable low-force resilient ring 146 or similar springdevice is provided to maintain the valve balls seated against the seatsexcept when pressurized air is flowing through the ports into thechamber 135.

An annular nozzle member 147 is fixedly secured within the outer end ofthe cylindrical chamber 143 and defines a converging-diverging nozzleopening 148 therein, this being commonly referred to as a Laval nozzle.A Laval-type nozzle is a nozzle with a throat and expanding exit so thatif a sufficient ratio of internal pressure to external pressure existsthe gases may expand beyond the throat, thus yielding supersonic speeds.In this invention, the nozzle opening 148 includes a converging upstreamportion defined by the tapered annular converging wall 151, with thisconverging nozzle portion being joined to a central nozzle portion ofminimal diameter as defined by the surrounding central cylindrical wall152. This central nozzle portion in turn communicates with a divergingnozzle portion defined by the surrounding tapered diverging annular wall153. This diverging portion 153 at its maximum diameter communicateswith a discharge nozzle passage 154 which, at its junction with thetapered wall 153, is of generally similar diameter. This dischargenozzle passage 154 is aligned with the nozzle and is axially elongated,and is defined by an axially elongate nozzle member extension 155 whichis fixed to and projects axially outwardly from the nozzle member. Thisnozzle member extension terminates in a discharge opening 160 at thefree end thereof.

The nozzle assembly further includes a control piston or valve 157 whichis of generally cylindrical cross section and is disposed within thecylindrical chamber 143 so as to be axially slidable therein, while atthe same time the slidable fit of the piston 157 within the chamber 143is such as to prevent any significant leakage past the walls thereof.This control piston 157 defines thereon a rear face 158 which is exposedto the pressure fluid (i.e. air) supplied through the air passage 142.The control piston 157, at the other end thereof, is provided with aseating face 159 which, in the illustrated embodiment, is of a truncatedconical configuration which converges as it projects toward the free endof the control piston, with the convergence being inclined similar tothat of the nozzle member wall 151 so that this seating face 159 canmove into substantially sealing engagement with the nozzle face 151.

The tubular part 138 is also provided with at least one and, in theillustrated embodiment, eight ports or orifices 156 which projectradially through the wall of the part 138 to provide for communicationbetween the storage chamber 135 and the control chamber 143. These ports156 communicate with the control chamber just upstream of the nozzlemember 147 and, as illustrated by FIG. 3, the front or lower end of thecontrol piston 157 has an end face (as defined by a part of the seatingface 159) which partially overlaps (or in fact may be disposedrearwardly of) the orifices 156 so that some of the pressure fluid instorage chamber 135 can pass through orifices 156 and act against thissmall-area rear face to exert a force on the control piston 157 tendingto move it (upwardly in FIG. 13) in an opening direction.

To supply pressurized air to the plurality of nozzle assemblies 133associated with each of the two rows on the head assembly 80', air istypically supplied from a pressure source S (FIG. 14) which may be aseparate compressor unit but which is typically the centralized airsupply as provided in a plant and is piped throughout the plant tovarious equipment. Such central air supplies typically are maintained ata pressure in the neighborhood of about 100 psi. The pressurized airfrom this supply S can be suitably supplied to the filter press througha main control valve 161 which can be utilized to turn on or off the airsupply to the nozzle assemblies associated with the press. Thepressurized air supplied through the control valve 161 is supplied to amain supply line 162 which in turn supplies a plurality of branch lines163, each having a control valve 164 associated therewith, the latterbeing a typical three-way valve which permits the pressurized supply airto be supplied either to a load (i.e., the nozzle assembly) or to theatmospheric (i.e., a discharge tank). Each branch line 163 containingits own control valve 164 in turn joins to a pair of individual supplylines 165, the latter being connected to an opposed pair of nozzleassemblies 133. In this illustrated embodiment, each opposed pair ofnozzles (that is, one of the nozzles in one row, and the directlyadjacent nozzle in the other row) are controlled by a respective valve164, but it will be appreciated that several pairs of nozzles (and infact all five pairs if desired) could be controlled by a single valve164 if desired. These individual supply lines 165 in turn communicatewith the respective air passages 142 associated with the nozzleassemblies 133. Each control valve 164 can also be shifted to allow thepassage 142 to communicate with a low-pressure drain or exhaust line166.

To use the nozzle assembly 133, pressurized air supplied to passage 142causes the control piston 157 to move into a closed position, and causespressurized air to flow into and build up within the closed storagechamber 135, thereby creating an isolated but confined volume (i.e. acharge) of pressurized air. When the pressure in passage 142 ismomentarily decreased to substantially atmospheric, such as by openingthe passage 142 to the exhaust or drain 166 by the control valve 164,then the pressurized fluid acting through ports 156 on the lower endface of control piston 157 causes this piston 157 to be rapidly movedupwardly into an open position, thereby opening the nozzle member 148,and then permitting the confined quantity of highly pressurized airwithin the storage chamber 135 to rapidly discharge through orifices 156with this air being effectively blasted through the nozzle member 148and then discharged through the opening 160 at a velocity whichapproaches or exceeds sonic velocity, with this blast of high velocityair occurring only for a very short duration which is significantly lessthan one second and, in fact is generally no more than about 100milliseconds.

The control valve 164 is also normally opened for a short duration oftime, such as about 100 milliseconds, and then can be immediatelyreclosed. At this time the pressurized air within chamber 135 hasalready been discharged, and hence pressurized air is again suppliedfrom the supply S into passage 142 to cause the control piston 157 toclose, and the chamber 135 to again be filled up with a further chargeof high pressure air.

Each nozzle assembly 133 in the illustrated embodiment is mounted to thehead member 131 by a suitable bracket assembly which permits the nozzleassembly to be both sidewardly and longitudinally adjustably tiltedrelative to the adjacent filter plate. This mounting arrangementincludes a bracket 167 which projects outwardly from the head member andemploys a horizontal swivel axis 168 which extends in the longitudinaldirection of the press. This bracket 167 in turn joins to a furtherbracket 169 which is secured to the storage tank 134 by a horizontalpivot axis 171 which extends perpendicularly relative to the axis 168.This enables the nozzle member of each nozzle assembly to be suitablytilted both longitudinally and sidewardly so as to be properly orientedrelative to the adjacent filter plate.

It will be appreciated that numerous variations can be made in thedesign of the nozzle assembly 133, specifically as to the design of thecontrol piston 157 and its positional and cooperative relationships withrespect to the supply passage 142 and the storage chamber 135. One suchvariation is illustrated by FIG. 15 which is structurally andfunctionally similar to FIG. 13 except that the ports 144 for supplyingpressurized air into the chamber 135 communicate directly with therearward end of the chamber 143, and the control piston 157 has anextension portion 157a which is slidably supported in the rearward orupstream end of the chamber 143 to close off the ports 144 when thecontrol piston is in the rearward or opened position during discharge ofthe storage chamber 135. This arrangement for the control piston 157effectively positively isolates the storage chamber 135 from the passage142 during the discharge phase, and additionally increases the responsetime of the control piston 157 in returning to its closed position sinceall of the pressurized air upon being resupplied to the passage 142initially reacts solely against the rearward end of the control pistonto at least initiate movement thereof toward the closed position, priorto permitting the supply air to be fed into the storage chamber 135.

This embodiment of the filter press also preferably includes platepositioning assemblies 175 disposed inside of but on opposite sides ofthe arch-shaped shifter housing for controlling the positioning of thefilter plate which is being moved from the closed stack into an openedposition when discharge of filter cake is desired. The plate positioningassemblies 175 as disposed on opposite sides of the shifter housing, inthe vicinity of but spaced upwardly from the opposite press side rails14, are identical and only one such assembly 175 will be described indetail.

Referencing specifically FIGS. 11 and 12, this positioning assembly 175is disposed adjacent the end of the arch-shaped shifter housing 22'which is opposite the shift units 41' and includes a small butvertically extending lower stop plate 176 which is fixedly secured to anupwardly projecting support 177. This latter support 177 is of agenerally Z-shaped configuration and includes a lower part which isvertically slidably supported on the housing 22' by suitable guides 178,with the upper part of support 177 being vertically slidably supportedon the housing 22' by further guides 179. The upper and lower portionsof the support 179 are joined by an intermediate horizontally extendingbight 181 to which is secured a downwardly projecting upper stop plate180. The bight 181 mounts thereon an upwardly projecting bracket whichjoins to a clevis 182 provided on the lower end of a piston rod 183which slidably projects downwardly from a conventional pressure cylinder184 (such as an air cylinder), the housing of which is secured to theshifter housing 22'.

The bight part 181 also mounts thereon a vertically swingable latchmember 185 which is hinged at 186 so that the latch member projectsgenerally horizontally in the upstream direction toward the stack ofclosed plates. The free end of the latch member defines a cam surface187 on the underside thereof which tapers downwardly in the openingdirection of the plates, and terminates in a rearwardly orientedshoulder 188.

When the plate positioning arrangements 175 are in a lowered positiondue to downward extension of the air cylinders 184, the lower stopplates 176 are positioned lowermost so as to be positioned for abutmentwith the handles 28' of the filter plate 17'-1 when the latter isshifted into the opened position and is spaced a predetermined distancefrom the opposed leading or endmost plate 17'-2 associated with theclosed stack. When in this opened position, wherein the handles of plate17'-1 abut the stop plates 176, this plate 17'-1 may still be spaced aslight distance from the endmost plate 17'-3 of the stack of opened andcleaned plates as disposed adjacent the movable head 15'. The upper stopplate 180 is positioned directly behind the upper corner of the openedplate 17'-1, specifically directly behind the top tabs 69' which projectfrom the upper corners of the plate, whereby the filter plate 17'-1effectively abuts against the top stops 180 and the lower stops 176. Atthe same time, as the plate is moved toward the stop plates, the upperedge of the filter plate engages the cam surface 187 and causes thelatch member 185 to pivot upwardly until the filter plate moves past thecam surface and substantially abuts the stop plates, whereupon theweight of the latch causes it to swing downwardly so that the shoulder188 effectively overlies and abuts against the front face of the filterplate adjacent the upper end thereof, whereupon the upper edge of thefilter plate is effectively captivated between the upper stops 180 andthe shoulders 188. This results in the opened plate 17'-1 being securelyand stationarily positioned prior to initiation of the air blastingoperation, and at the same time ensures that this plate is positioned apredetermined distance from the opposed plate 17'-2. This maintaining ofa predetermined spacing between the two opposed plates 17'-1 and 17'-2can become significant in presses employing a large number of platessince, in such instance, it has been observed that the length of theclosed stack of plates when in the closed filtration stage can beseveral inches less than the stack of plates positioned adjacent themoving head after emptying of the press. Thus, if the opened plate isalways moved over into engagement with the stack of empty plates, theopening distance can progressively decrease throughout a cycle by asmuch as several inches from beginning to end, and such decrease caneffect proper positioning of the nozzle assemblies relative to thefilter plates.

The operation of the filter press according to the embodiment of FIGS.11-14 is substantially the same as the operation described above. Theportions of the operation which are different, specifically the portionsof the operation as effected by the air-assist discharge mechanism 62'and the stop arrangements 175, however, will be briefly described.

When the filter press is to be emptied, the leading plate in the closedstack will be shifted into an opened position by the shifter assembly41' in the same manner as described above relative to FIGS. 1-8. Thatis, the shifter cylinders are energized to cause the shifter plate 47'to engage the handles 18' of the endmost plate and then slidably shiftthis plate along the rails 14' into an opened position substantially asdepicted by the plate 17'-1 in FIG. 11. In this embodiment, however, theair cylinders 184 of the plate positioning arrangement 175 have beenpreviously energized downwardly to lower the stop plate 176 and 180, andthe filter plate 17'-1 is shifted into an opened position until theplate substantially abuts the stop plates 176 and 180, at which time thelatch members 185 also swing downwardly and engage the upper edge of theopened plate. As the shift cylinders extend so as to move the frontmostplate 17'-1 into the opened position, as this plate closely approachesthe opened position, the shifter plate 47' contacts a limit switch whichis mounted on the shifter housing in close proximity to the openposition, causing activation of this limit switch. This transmits asignal to the controller 93 which turn transmits a signal terminatingthe forward extension of the shift cylinders. At that time a furthersignal is transmitted from the controller to the air discharge assembly62' so as to initiate the operation thereof. The air cylinder 104'associated with the scissor mechanism 109' is energized to cause thescissor mechanism to extend downwardly and move the head assembly 80'downwardly between the opposed filter plates. Upon reaching the lowerposition, the cylinder 104' is reversely energized to retract the headassembly 80' back up into its uppermost position, thereby completely thecleaning cycle.

During the cyclic actuation of the head assembly 80', the nozzleassemblies 133 are preferably discharged several times at short timedintervals, preferably but optionally on both the downstroke and upstrokeof the head assembly 80'. For example, each row of nozzle assemblies 133will normally be first discharged just prior to or shortly after theinitiation of downward vertical movement of the head assembly 80' sothat high velocity air blasts are directed against the upper edges ofthe filter plates to assist in peeling the upper edge of the cake awayfrom the underlying membrane or diaphragm. As the nozzle assemblies 133are moved downwardly, the storage tanks 134 rapidly recharge, and thenozzle assemblies 133 are repeatedly discharged preferably at leastthree or four times as the head assembly 80' moves downwardly, with thelast discharge being substantially at or adjacent the lowermost positionof the head assembly so that an air blast can be directed against thelower portion of the filter plate diaphragms. It has been experimentallyobserved that the air discharges can occur at short time intervals, suchas at about two second intervals, as the head assembly moves downwardly,and again similarly on the upstroke if desired.

The control for the sequential blasting of high velocity air pulses fromthe nozzle assemblies 133 originate from the controller 93 which can besuitably programmed to provide desired timing between adjacentdischarges, and which provide timed activation of the control valves 164so as to permit discharging of the supply passages 142 for a shortduration, such as in the order of about 100 milliseconds, which issufficient to allow each control piston 157 to shift into an openposition and permit discharge of the respective charge of high pressureair stored in the respective storage chamber 135.

In addition, by providing each pair or grouping of nozzle assemblies 133with its own respective control valve 164, then these control valves 164can also be provided with control signals from the controller 93' atslightly different or delayed times so as to cause the various nozzleassemblies 133 within each row to be discharged in a slightly delayedand sequential manner relative to one another. This slightly delayed andsequential discharge of the nozzles within the row not only tends toreduce noise generated by the overall arrangement, but is also believedto provide additional turbulence and agitation transversely across thefilter plate so as to possibly assist in dislodging the sticky cake fromthe membrane.

After the head assembly 80' completes the air discharge assist operationand returns to its raised position, then this transmit a signal to thecontroller 93' which in turn then transmit a signal to the shiftcylinders so that the shift plates 47' are slightly retracted back intoan intermediate position substantially as illustrated by the dotted lineposition in FIG. 11, and then transmits a signal to cylinders 184 whichcause them to raise upwardly and lift the stop plates 176 and 180, andsubsequentially a signal is transmitted to the shifter mechanism 41' toreinitiate the forward extension of the shift cylinders so that theshift plates 47' again engage the front filter plate 17'-1 and thenshift it forwardly into engagement with the endmost plate 17'-3 of theopen stack. The shifter mechanism then returns to its initial position,at reach position the shifter housing is shifted rearwardly until aproximity switch senses the presence of the handle on the next plate andstops the movement. The entire shifter housing and related mechanismsare now in position to permit initiation of a further cycle in the samemanner as described above.

The filter press of the present invention, when incorporating thefeatures of the second embodiment as illustrated by FIGS. 11-14, willalso preferably but optionally include the bumping or vibrating devices61 as previously described.

In addition, when using the air discharge assist mechanism 62',particularly on presses which employ relatively small filter plates, itis anticipated that the vertical traverse of the nozzles downwardly andupwardly along the filter plates may be eliminated, and instead thenozzles can be stationarily positioned adjacent the upper edge of theopened plates and utilized to discharge at least one, and preferably twoor three, high velocity short duration air blasts downwardly against theupper edges of the filter cake to assist in discharging the cake fromthe plates.

In an exemplary embodiment of a filter press employing the air-assistdischarge mechanism 62', the nozzle assemblies 133 will each have aseparate storage chamber 135 having an air capacity which is preferablyin the range of from about 0.1 to about 0.3 cubic feet, the charge ofair which accumulates within the storage chamber 135 will have a maximumpressure which is preferably in the range of from about 80 to 120 psi,the control valve 164 for the respective nozzle assemblies will beopened for a time interval which will preferably be no greater thanabout 150 milliseconds, and typically in the range of from about 50 to150 milliseconds to permit rapid and complete discharge of thepressurized air charge from the storage tank through the respectiveLaval nozzles, and the nozzle assemblies will be repeatedly dischargedduring each cake release cycle at short intervals in the range of fromabout one to about three seconds and preferably at about two secondintervals.

While the invention as described above utilizes a separate air storagetank 134 for each nozzle 148, it will be appreciated that a single airstorage tank may be provided for a grouping of nozzles, with the tankstorage capacity being appropriately sized in accordance with the memberof nozzles which are supplied with air therefrom. Such tank or tanks,however, are preferably mounted on the head assembly so as to bedisposed in close proximity to the nozzles 148. Each such nozzle 148should still preferably have its own control piston 157 associatedtherewith.

Additionally, while the invention as described above utilizes the platepositioning assemblies 175 for stopping the shifted plate at apredetermined distance from the remaining stack of plates, it will beappreciated that in some presses such plate positioning assemblies 175can be eliminated and the shifted plate positioned directly adjacent thepreviously shifted plates prior to initiation of the air dischargecycle. In situations where the dimensional variation between the closedplate stack dimension and the opened plate stack dimension isinsignificant, then the plate positioning assemblies 175 can beeliminated.

Further, while the press as described above utilizes support rollersdisposed in engagement with elongate support rods, with one of therollers being a frictional drive roller, such as the roller 32 and itsdriving engagement with the rod 25, nevertheless other types of drivedevices can be provided. For example, the drive can comprise a gear-rackarrangement wherein the gear is mounted on the shifter and replaces thedrive roller 32, and is disposed in rolling engagement with an elongaterack which is fixed to and extends horizontally of the press along oneof the side rails 14.

Although a particular preferred embodiment of the invention has beendisclosed in detail for illustrative purposes, it will be recognizedthat variations or modifications of the disclosed apparatus, includingthe rearrangement of parts, lie within the scope of the presentinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. In a filter pressincluding a frame having a pair of horizontally elongate and generallyparallel side rails which extend lengthwise of the press and aresidewardly spaced apart, a first head structure stationarily mountedadjacent one end of said rails, a second head structure mounted on saidrails for movement toward and away from said first head structure forrespective closing and opening of said press, a plurality ofvertically-enlarged filter plates movably disposed in generallyside-by-side relationship to define a stack extending lengthwise betweensaid first and second head structures when said press is closed, eachsaid filter plate mounting thereon a respective filter member which isindependent of the filter members mounted on the other filter plates,said filter plates extending transversely between and being slidablysupported on said side rails, each movable filter plate having partswhich project outwardly from opposite side edges thereof, and a shiftassembly for effecting shifting of individual said filter plates alongthe side rails toward the second head structure when said second headstructure is in an open position, the improvement comprising:dischargeassist means for directing a pressurized stream of air against anexposed face of an endmost said plate of said stack to assist indislodging filtrate adhered to said plate, said discharge assist meansincluding an air nozzle assembly for directing a pressurized airstreamat the exposed face of said plate, and a drive device for moving thenozzle generally parallel across the face to effect air-assisteddischarge throughout the entirety of the face.
 2. A filter pressaccording to claim 1, wherein said discharge assist mechanism includesmeans for causing the pressurized streams of air to be generated as aseries of spaced but short duration air blasts having a velocitygenerally near sonic velocity.
 3. A filter press according to claim 1,wherein said air nozzle assembly includes a plurality of nozzle meansfor discharging short duration blasts of air against the exposed face ofthe filter plate.
 4. A filter press according to claim 3, wherein thenozzle means defining a Level-type nozzle for discharging air at avelocity generally near sonic velocity.
 5. A filter press according toclaim 3, wherein each said nozzle means includes a discharge nozzledisposed adjacent and oriented toward the exposed face of the filterplate and a separate air storage tank disposed adjacent and in fluidcommunication with the respective discharge nozzle, said storage tankdefining therein a closed low-volume storage chamber for containingtherein a quantity of highly pressurized air, said discharge nozzleincluding a converging-diverging configuration for discharging the airat a velocity which at least approaches sonic velocity, and shiftablecontrol means for normally isolating the pressurized air in the storagechamber from the discharge nozzle and permitting the quantity ofpressurized air in the storage tank to be blasted through the dischargenozzle when the shiftable control means is moved into an open position.6. A filter press according to claim 5, including means for supplyingpressurized air into the storage chamber when the shiftable controlmeans is in a closed position, and said nozzle means including means forisolating said storage chamber from said supplying means when theshiftable control means is in said open position.
 7. A filter pressaccording to claim 6, including controller means for effectingsequential discharge of said nozzle means at timed intervals of shortduration.
 8. A filter press according to claim 7, wherein said shiftablecontrol means includes a pressure-moved control member having a firstpressure face acted on by the pressurized air supplied by said supplyingmeans for normally maintaining the control member in the closedposition, said control member having a second pressure face which isacted on by the pressurized air in said storage chamber, said secondpressure face being opposed to and of smaller area than said firstpressure face to cause the control member to be shifted into the openedposition when the supply pressure against said first face is relieved.9. A filter press according to claim 1, wherein the shifter assemblyincludes a plate shifter mechanism for effecting slidable shifting of anendmost plate from the stack along the support rails away from the stacktoward the open second head structure into an opened position spaced apredetermined distance from a remaining endmost plate of the stack todefine a gap therebetween;said shift assembly including a shifterhousing which is movably supported on said frame for movement lengthwisethereof, said shifter housing mounting said plate shifter mechanismthereon; said discharge assist means being mounted on said shifterhousing adjacent a side of said gap, and said discharge assist meansincluding first and second said air nozzle assemblies which arerespectively positioned for directing airstreams against exposed facesof the plates defining opposite ends of the gap; and plate positioningmeans mounted on said shifter housing and including plate-contactingstop means movable from an inactive position spaced from the path ofmovement of the filter plates to an active position wherein the stopmeans are disposed for contacting the filter plate which is disposed insaid opened position to prevent the plate from moving past the openedposition.
 10. A filter press according to claim 9, including a motivemeans controlled by said controller means for moving said stop meansinto said inactive position after the airstreams have been dischargedagainst the plates and for initiating forward movement of said shiftermechanism to move said opened plate forwardly from said opened positiontoward the open second head structure.
 11. A process for dischargingfiltrate from filter plates of a filter press, comprising the stepsof:providing an elongated stack of upright filter plates positioned inadjacent, side-by-side contacting relationship; moving an endmost plateof said stack a predetermined distance away from the stack to define agap between said endmost plate and a next adjacent plate of said stack;providing a discharge assist means for discharging a series ofshort-duration air blasts at a velocity which at least approaches sonicvelocity; simultaneously discharging said series of short-durationhigh-velocity air blasts against the opposed exposed faces of saidendmost and next adjacent plates to assist in removing filtrate adheredto said opposed exposed faces; and sequentially repeating the abovesteps.
 12. A process according to claim 11, including the stepsof:providing a plurality of nozzles laterally adjacent one side of saidgap on said discharge assist means; moving said plurality of nozzlesinto said gap so that the nozzles are moved in spaced but generallyparallel relationship across the opposed exposed faces; and directingsaid air blasts from said nozzles against the opposed exposed faces asthe nozzles are moved therealong.
 13. A process according to claim 12,wherein the series of short-duration high-velocity air blasts aredischarged from said nozzles in spaced times intervals as the nozzlesare moved cross the opposed exposed faces.
 14. A process according toclaim 13, including the step of transversely bumping solely the nextadjacent plate to at least partially loosen filtrate adhered to saidplate prior to moving said next adjacent plate away from the stack. 15.A process according to claim 12, including the step of transverselybumping solely the next adjacent plate to at least partially loosenfiltrate adhered to said plate prior to moving said next adjacent plateaway from the stack.